Identification of and distinction between the scales of South African pilchard Sardinops ocellatus and Cape anchovy Engraulis capensis

Abstract

Fossil fish scales hold potential for elucidating past fluctuations in fish populations. Only certain pilchard Sardinops ocellatus and anchovy Engraulis capensis scales can be distinguished easily from each other. Misidentification of the less-typical scales of the two species can introduce a bias in scale-based population studies and, in order to overcome this bias, scales removed from pilchard and anchovy reared in captivity were examined. A complete set of reference photographs of the scales of each species was compiled and study of these showed that both pilchard and anchovy have five distinctive scale types, each of which is found on different parts of the fish. It was also shown that the "typical" scales of each species, i.e. those referred to in the literature, constitute less than 50 per cent of the scales found on the fish.